Would you say the person respnsible is a cat burglar?

Now this is news!

Yep sounds like OP’s dual boot issues are due to installing windows last. It only overwrites boot each startup if it doesn’t have its own boot partition.

Also try btrfs on your linux partition for better interop. Somehow, windows btrfs drivers are much more mature than windows ext4 or linux ntfs drivers.

There is also nonsteamlaunchers but I haven’t tried it on desktop. Full disclosure, even on steam deck I swapped back to lutris because updating was clunky. Still, might be an option for you.

Grandma died